Lack of Fusion Detection

Lack of fusion is one of the most detected discontinuity by UT pulse echo method, conventional or Phased Array mode. Sometimes welders ask that during repair this was not possible to ¨see¨ any discontinuity during grinding or gouging. It is important to take in mind that lack of fusion could be extremely tight and is not possible to detect by non controlled destructive methods.
In the image a extremely small lack of fusion in an austenitic steel weld, that could not be seen without a carefully destructive examination.